GB1026010A - Improvements relating to fuel elements for nuclear reactors - Google Patents

Abstract

1,026,010. Fuel elements. ARBEITSGEMEINSCHAFT VERSUCHS - REAKTOR (A.V.R.) G.m.b.H. March 16, 1965 [March 25, 1964; Oct. 7, 1964; Feb. 13, 1965], No. 11150/65. Heading G6C. A nuclear reactor fuel element comprises a graphite sphere formed at a position spaced from its centre with an internal chamber containing fissile material, e.g. uranium particles coated with pyrolytic graphite, the chamber in the examples described being annular and extending symmetrically around an axis passing through the centre of the sphere. The fuel element (Fig. 1, not shown) may comprise two graphite hemispheres 1, 2 interconnected by a graphite stud 3 formed with two sets of screwthreads, one to each hand. Each hemisphere is formed with an annular recess 11, 2<1> which cooperate to give an annular chamber which receives coated uranium particles 4. An annular graphite closure plug 6 acts as a screen between the uranium particles 4 and the boundary 5 between the two hemispheres. In an alternative embodiment (Fig. 3, not shown), an externally screw-threaded graphite plug 9 is screwed into a blind bore 8 in a graphite sphere 7. The plug 9 is formed with an annular chamber 10 which receives coated uranium particles 4, an annular graphite closure plug 6 being located in the outer end of the chamber 10. The two graphite hemispheres of a further embodiment (Fig. 5, not shown) are interconnected by a screw-threaded stud 13<1> which is an integral part of the hemisphere 11, each hemisphere having a recess which co-operate to form an annular chamber having the shape of a double frusto spherical shell. The hemisphere 11 has an annular step 17 which engages in a mating recess at the edge of the hemisphere 12 in order that no continuous gap may be formed at the boundary between the two hemispheres when the stud 13<1> becomes very hot. The annular plug which acts as a screen between the uranium particles 14 in the annular chamber and the boundary between the two hemispheres 11, 12 may be made of a carbon fibre material, such as felt, fabric, wadding or wool. Alternatively, the annular chamber may be in the shape of two frusto cones the larger diameter ends of which abut one another at a hemispherical plane of the sphere. In either case, the walls of the recesses extend perpendicular to the boundary plane between the two hemispheres, where they meet the boundary plane, to provide a smooth transition between the two parts of the chamber across the boundary plane.